Although this year's flu season has nothing of last year's most deadly influenza in the last decade, alertness is always important, say infectious disease and public health experts.
Local and government reports prove this In the Bay Area, the flu season is in full swing. The first deaths were announced this month. Now that the flu is back in circulation, doctors, nurses and public health officials are monitoring key monitoring reports to prepare for the upcoming season.
"The flu brings no news like last year's pandemic. But it's definitely out there, "Dr. Jeffrey Silvers, Sutter Health Infectious Diseases Medical Director. "We're still going to make many people sick and many people die."
Many of the reports that follow experts like Silvers are public and reasonably accessible, even to the amateur epidemiologist at home. Here are descriptions of three of these reports and what they are saying about the season so far.
Influenza-like disease: The US Centers for Disease Control and Prevention collect reports from a network of hospitals, clinics, and other health care providers that should reflect on what's happening in the rest of the country. Among her reports is the percentage of all outpatient visits that have flu-like symptoms, especially fever, cough, or sore throat.
It is not an accurate measure of the actual number of people suffering from the flu; This number is almost impossible to get, as most people who have the flu do not go to the doctor. But there is a reasonable feeling for the big picture: If people appear in doctors' offices with fever and sore throats at this time of year, it is a good bet that some of them have the flu. As this number increases, it means more flu is circulating.
Outside the flu season, the percentage of influenza-like illnesses (ILI) is between about 1 and 2 percent. It usually rises over 2 percent in November, reaching between 3 percent – a very mild year – and 8 percent. Last year, the ILI percentage reached 7.5, which was comparable to the infamous "swine flu" season from 2008 to 2009.
The percentage on January 12 – the last available report – was 3.1, well below 5.9 at the same time last year. But the season is far from over.
"You do not know if a low level of activity means you will have a good year, or you have not reached a high level yet," Dr. Jonathan Blum, specialist in infectious diseases at Kaiser Permanente Santa Clara. "It would be premature to say that we will get away easily this year."
Viral Stem: There are hundreds of influenza strains, but usually only four or five circling in a typical flu season. with one of those who dominate. Which strains are in circulation because some cause more serious diseases than others, and the efficacy of the flu vaccine is very different between the strains.
One reason for the past year was that the predominant strain was Type A, so the subtype H3N2 is known to be particularly virulent and not well matched to the flu vaccine. This year, the dominant strain is type A subtype H1N1. This is the so-called swine flu strain, and although it was first reported in 2008 and 2009, it caused a relatively mild illness in most people.
The burden on an individual is rarely significant – Unless it is known that a particular strain is resistant to antiviral drugs, treatment will be the same regardless of type. However, experts will use the national and regional reports as another tool to prepare for the season. If it is a H1N1 year, there is likely to be a normal recovery in winter office visits. If it is a H3N2 year, public health officials can make plans for triage tents in emergency rooms.
Infectious disease experts are also looking for mutant strains, especially in ways that can make them more dangerous. In Japan, for example, there are previous reports of antiviral resistance in H3N2 strains. It is not too worrying yet, but scientists will be watching.
"We want to know in real time about an unusual or novel burden," said Dr. Erica Pan, Interim Health Officer of the Public Health Department in Alameda.  Deaths: Infectious disease experts believe nationwide that about 80,000 people died from the flu last year. But that's an estimate, not an actual number.
No one detects every flu death every year – the number is too high. Instead, several local and national authorities will monitor influenza-related deaths in specific age groups and use this data as another marker of the severity of a particular season and extrapolation of total mortality.
In California, the Department of Public Health used to do this The counties must report all flu deaths among persons under 65 years of age. Although people over the age of 65 are most susceptible to the flu, reporting their deaths is problematic for two reasons: it would take too much time and money, and their cases often become complicated many times over Health problems that kill the flu shoot ,
Earlier this year, the Public Health Department stopped calling for counties reporting influenza deaths in adults. Instead, the state monitors deaths below the age of 65 by looking for death certificates that listed the cause of the flu as a cause of death.
The move means that the death toll this year can not be directly compared to California. In fact, the total number of deaths this season (75) is higher than at the same time last year (74), although the last year was a much grippier flu season.
Aside from educating public health officials and doctors about the course of the season, the flu death counts for another purpose: they are a pathological remedy to remind the public to take the flu seriously.
"People still do not have healthy respect for the flu. Pan said. "It's a real thing that kills people every year."
The Snack: So what should the average person do with all this information? Not necessary. As experts for infectious diseases like to say, the flu is predictable only because of its unpredictability, and even a seemingly mild year can get angry without much warning.
That means there are precautions: Wash your hands frequently. Do not go to work or school if you have a fever, cough, or sore throat. Call your doctor if you think you may be suffering from the flu.
And yes, there is still time to get a flu shot.
Erin Allday is a writer of the San Francisco Chronicle. E-mail: email@example.com Twitter: @erinallday